The objective of this proposal is to determine the role of calcium ions in the mechanism of action of gonadotropin releasing hormone (GnRH) stimulated release of luteinizing hormone (LH) from the pituitary. This objective will be obtained by analysis and manipulation of calcium movement, localization of calcium binding and contractile proteins, blockade and activation of calcium target proteins, direct measurement of cellular calcium potentials, and determination of specific sites of calcium action in response to stimulation by GnRN in pituitary cell gonadotropes.